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Zacharias Janssen

From Wikipedia, the free encyclopedia


Zacharias Janssen (also Zacharias Jansen or Sacharias Jansen) (1585 – pre-1632) was a Dutch spectacle-maker from Middelburg associated with the invention of the first optical telescope. Janssen is sometimes also credited for inventing the first truly compound microscope. However, the origin of the microscope, just like the origin of the telescope, is a matter of debate.

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Zacharias Janssen was born in The Hague. Local records seem to indicate he was born in 1585 although a date of birth as early as 1580 or as late a 1588 are also given. His parents were Hans Martens (who may have had the occupation of a peddler) and Maeyken Meertens, both probably from Antwerp, Belgium. He grew up with his sister Sara in Middelburg, at the time the second most important city of the Netherlands. He was known as a “street seller” who was constantly in trouble with the local authorities.

He stated he was born in The Hague on the marriage file of his first marriage, with Catharina de Haene, on October 23, 1610. When this file was refound by Cornelis de Waard in 1906, De Waard found the following excerpt: Sacharias Jansen, j.g. uut Den Haag, “Zacharias Jansen, bachelor from The Hague” Before, it was often thought that Janssen was a native of Middelburg. In 1612, Zacharias and Catharina had a son they named Johannes Zachariassen.

In 1615 Zacharias was appointed guardian of two children of Lowys Lowyssen “geseyt Henricxen brilmakers” (called Henry the spectacle maker). It is surmised that Zacharias also took possession of Lowys Lowyssen’s spectacle-making tools because the first record of Zacharias Janssen being a spectacle maker appears in 1616. The family had to move to Arnemuiden in 1618 after Zacharias’s counterfeiting activities were exposed. There Zacharias was again accused of counterfeiting in 1619 causing him to be on the move again, ending up back in Middleburg in 1621.

A year after the death of Janssen’s first wife in 1624, he married Anna Couget from Antwerp, who was the widow of a Willem Jansen (probably a relative of Janssen). He moved to Amsterdam in November 1626 with a profession of a spectacle maker, but was bankrupt by 1628. Janssen has been given a death date as late as 1638 although his sister said he was dead in 1632 testimony and his son Johannes declared his parents had died by the time of his marriage in April 1632.

Claimed Inventions

Over the years there have been claims Zacharias Janssen invented the telescope and/or the microscope in Middelburg between 1590 and 1618. Zacharias worked for some period of his life as spectacle-maker (a very competitive and secretive trade) and at one time lived next door to Middelburg spectacle maker Hans Lippershey, also claimed to have invented the telescope. Janssen’s attribution to these discoveries is debatable since there is no concrete evidence as to the actual inventor, and there are a whole series of confusing and conflicting claims from the testimony of his son and fellow countrymen, in different testimony in 1634 and 1655.


Janssen has been associated with the invention of the single-lens (simple) optical microscope and the compound (2 or more lens) 9x magnification optical microscope, sometimes claimed to have been devised with the help of his father (or sometimes said to have been built entirely by his father) with a date of invention commonly given as 1590 (or sometimes 1595), while trying to find a way to make magnification even greater to help people with seriously poor eyesight.


Janssen is one of three people who have been associated with the invention of the telescope in the Netherlands in 1608. That year Hans Lippershey filed the first known patent for the device on October 2 with the States General of the Netherlands, followed a few weeks later by a second patent application by Jacob Metius of Alkmaar. Both were turned down because there were counter claims for the invention.

Varying accounts are cited to support Janssen as a possible inventor of the telescope. German astronomer Simon Marius wrote an account to his patron Johan Philip Fuchs von Bimbach about meeting an unnamed Dutchman at the 1608 Autumn Frankfurt Fair (which ran the month of September) who tried to sell him a device that sounded like a telescope. Given his history as a street seller, there is speculation this unnamed Dutchman could have been Zacharias Janssen, which would mean Janssen had a telescope at least a month before Lippershey’s October 2, 1608 patent date. William de Boreel, who visited Middelburg to research the invention in 1655, interviewed Janssen’s son Johannes. Boreel concluded that Janssen’s telescope was finished about 1610. His research was referenced by Pierre Borel in De vero telescopii inventore. There are other claims that Janssen constructed the first telescope in 1604, or even earlier. Janssen’s son Johannes testified under oath that Hans Lippershey had stolen his father’s invention of the telescope, and that his father had invented the device in 1590.



Reproduction of an optical device that Zacharias Snijder in 1841 claimed was an early telescope built by Jansen. Dutch biologist and naturalist Pieter Harting claimed in 1858 that this was an early microscope which he also attributed to Janssen, perpetuating the Janssen claim to both devices. Its actual function and creator has been disputed.

The confusion surrounding the claim to invention of the telescope and the microscope arises in part from the (sometimes conflicting) testimony of Zacharias Janssen’s son, Johannes Zachariassen. Johannes claims include that his father invented the telescope in 1590, that his father invented the telescope in 1604, that he and his father invented the telescope in 1618, and that Jacob Metius and Cornelis Drebbel bought a telescope from him and his father in 1620 and copied it. Johannes also seems to have lied about his own date of birth, maybe so he could stake his own claim as inventor of the telescope along with his father.

The 1655 investigation by William Boreel (who may have been a childhood friend of Zacharias Zachariassen) added to the confusion over invention. The people he interviewed were trying to recount details 50 or 60 years after the fact and Boreel may have confused the names of spectacle makers from his childhood. He may have also been confused about a microscope built by another optician for Drebbel, claiming it was built by Zacharias Janssen.

Albert Van Helden, Sven Dupré, Rob Van Gent, and Huib Zuidervaart in their book “Origins of the Telescope” came to the conclusion that Janssen may not have become an optician until 1616 and that the claims surrounding him as the inventor of the telescope and the microscope were the fabrications of his own son, Johannes Zachariassen, who claimed it as a matter of fame and for possible financial gain.

Illegal Activities

In the years 1613–1619, Janssen was tried several times for counterfeiting coins. Janssen grew up right next to the Middleburg mint where his brother-in-law worked. These circumstances made it very easy for Janssen to mimic the process of manufacturing money. He fled to the neighbouring village of Arnemuiden to avoid the high penalties for counterfeiting coins.

However, he continued counterfeiting coins in Arnemuiden. In 1619 he was apprehended for owning several devices he counterfeited coins with. Normally, one would have been sentenced to death for this crime. However, since the father of the Arnemuiden bailiff was found to be an accessory, he was pardoned from this punishment. Thanks to this, the process was delayed to such an extent that Janssen was able to flee again. Eventually, the case was dismissed. Janssen returned to Middleburg in 1621.

Historical Record

Janssen’s life was documented by the many investigations on the subject before the Second World War. Many of the Middelburg archives were destroyed by a bombing of Middelburg on May 17, 1940, during the Nazi invasion of the Netherlands. Without these earlier studies, very little would be known of Janssen’s life at all, since all original files were lost in the fires following the bombardment.